- About using the AO as a focus. Frequently the sharpest focus is not necessarily where you need to set your AO adjustment. The AO is all about reducing parallax. If you move your head/eye a little and your cross hair appears to move on the target your AO is not adjusted correctly.
- Fixed parallax scopes. At one thime MOST centerfire scopes had their scopes set parallax free at 100 yards (rimfire scope are set at 50 yards). For the past few years companies have been using different parallax free distances, frequently it's 150 yards, others may use other distances.
